1. Field of Invention
The present invention relates to gems and, more particularly, to a process for detecting the presence of organic compounds which have been used as enhancement/treatment agents to fill surface reaching fissures, fractures, pores and imperfections in gemstones.
The process of the present invention uses Near Infrared (NIR) and Mid Infrared (MIR) radiation, reflected diffuse energy and spectroscopic analysis to detect the presence of organic fillers.
2. Art Relating to the Invention
Gems are a category of minerals that exhibit a unique set of physical and optical characteristics that are reflected in their color, clarity, hardness, degree of transparency and dispersion. These attributes blend together with related properties to define the beauty, desirability and rarity that define a gemstone's desirability and market value. In most cases, with the exception of pearls and related organic material, gems are generally cut and polished for ornamental purposes. Natural materials can be replicated in the laboratory by various techniques that are typically referred to as laboratory grown or synthetic products. Because of the extreme geochemical conditions of gem material formation, structural issues at an atomic level and the methods of recovery, many gems contain surface reaching fissures, fracture systems and porosity. The presence of imperfections and blemishes can significantly decrease the value of a gem in the market place. For example, two of the most costly chromium-bearing gems, Ruby and Emerald, typically contain surface reaching fissures and fractures that impact on their value. It is a common practice in the jewelry industry to enhance a gem's appearance and subsequently its beauty, by filling these imperfections with foreign substances, thereby altering the appearance of the reflecting and visually distracting surface reaching fractures.
Organic compounds which are conventionally used to enhance the beauty of gems include oils, waxes, epoxy resins and other natural and synthetic resins. These organics are generally undetectable to the human eye. By selecting fillers or enhancement/treatment agents with optical characteristics similar to that of the gemstone, the effectiveness of the masking agent is increased. For example, a Colombian Emerald with a characteristic refractive index of 1.569–1.577 can effectively be altered by using EPON 828, an epoxy resin that has a similar refractive index of 1.573. This near match can create the illusion of significantly greater value. The improvement in appearance can make the difference between a salable and non-salable item and potentially increase the market value of the end product by thousands of dollars. Although commonly sold without disclosure of these additives, the Federal Trade Commission and other government agencies mandate full disclosure of all enhancement agents that are not permanent and ultimately affect the economic position of a consumer.
Infrared spectroscopy has been employed to examine gems in the past. Typically, the gem is placed in front of an infrared radiation source and a detector is positioned behind the gem to capture radiation that is transmitted through or emitted from the gem. The radiation source and the detector being in the same line of sight. Due to the scattering of the radiation, the captured radiation does not always provide an adequate “finger print” of the enhancement/treatment agents identity or indicate the quantity of the organic filler present.
Another method suggested for detecting organic compounds in gemstones has been Raman Spectroscopy. The Raman microprobe is a laser based analytical device that has been used to detect organic fissure filling, clarity enhancement agents. Althouh it offers good spatial resolution, it only analyses specific inclusions or points along a fracture and not the total gem simultaneously. The equipment is expensive and implementation of the technique is labor intensive and tedious. In addition, minerals that fluoresce, like ruby, are not good candidates for Raman analysis. Aggregate materials like turquoise, jade and pearl are equally problematic because of excessive signal scattering.
There is a need for a quick, simple means to detect the presence opf organic compounds in gemstones.